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Northwest PA Bolens Fan!
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315 Posts
Discussion Starter #1
Hey Gang!

It looks like I bought a bad coil on E-bay. Here is the story...tell me if I'm missing something.

I have a Tecumseh HH140 (overhead valve) in a 1973 Bolens G14. It ran fine up until a couple of weeks ago, then suddenly had no spark.

I disconnected the 3-wire harness from the tractor to isolate the engine from the tractor circuit. The flywheel trigger pins and the air gap (.008 inch) are good. I even removed the spark plug boot to check for spark directly from the high tension wire. I pulled the flywheel to check the magnets and keyway and everything seems to be in order there.

Based on the above actions, I figured that the coil had gone bad. E-bay to the rescue with a used coil for $81 and---you guessed it---still no spark.

I measured the resistance on both coils and these are the results. Perhaps someone can make some analysis of these numbers.

ORIGINAL COIL

Engine ground to Ground Terminal: Open
Ground Terminal to High Tension Lead: Open
High Tension Lead to Engine Ground: 5.08 K

E-BAY COIL

Engine ground to Ground Terminal: 3.8 M
Ground Terminal to High Tension Lead: Open
High Tension Lead to Engine Ground: 5.45 K

Am I missing something? It seems pretty simple...rotating magnets past the coil and it is supposed to spark. Anybody have any other ideas?

Thanks!
 

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Northwest PA Bolens Fan!
Joined
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315 Posts
Discussion Starter #2
UPDATE: More INFO on the Tecumseh with no spark

Update! I have spark! It turns out that the E-bay coil is good.

Due to some confusing posts and conflicting information I've read about the Tecumseh ignition system, my understanding of the system was a little flawed. I know that the ignition switch on these engines grounds out the coil in the OFF position. I interpreted this to mean that the ground wire from the ignition switch is wired directly to the small lead on the coil. This belief was supported by statements I've read that say the stator under the flywheel is strictly for charging the battery, and that the coil (solid state ignition unit- or SSI) is entirely self-contained and a stand alone system.

THIS IS NOT THE CASE! Even the "modern" OHV tecumseh with the solid-state ignition utilizes two posts on the stator to provide voltage to the coil. The ground wire from the ignition switch goes to the charge coils in the stator, and the charge coil is wired to the small lead at the coil.

I read that to troubleshoot this system, one only needed to disconnect the 3-pin electrical harness from the engine to isolate the tractor's wiring from the engine's wiring. This is true. However, the small lead MUST be connected to the coil or the voltage from the charge coils in the stator will never make it to the coil.

Now that I have the proper understanding of the system, I have all kinds of spark! The next thing I'm going to do once I get the tractor back together is put my hydraulic system to work. I'll post a link to Youtube once I figure out how to upload a video showing my hydraulic system in action. Here is the link showing the fabrication of that system.

http://picasaweb.google.com/tedrmiller/BolensG14HydraulicUpgradeProject?feat=directlink

Thanks for all the great information...I hope my experience here will help someone else. Also, many thanks to Ed Stoller for his ignition work and his website. Without it, I'd still be scratching my head and mowing with my push mower!

http://home.earthlink.net/~edstoller/

Good Day!

Ted
 
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